Abstract:

A multimedia data system comprising a synchronization unit. The
synchronization unit receives a demodulated bitstream, checks whether a
FAW pattern corresponding to a candidate of the bitstream exists, checks
whether an additional information corresponding to the candidate of the
bitstream is valid when the FAW pattern exists, determines a hit
weighting corresponding to the candidate according to the checking
result, determines whether the hit weighting meets a criterion and
outputs a synchronization signal when the hit weighting meets the
criterion.

Claims:

1. A synchronization method, comprising:receiving a bitstream;checking
whether an FAW pattern corresponding to a candidate of the bitstream
exists;checking whether an additional information corresponding to the
candidate of the bitstream is valid when the FAW pattern
exists;determining a hit weighting corresponding to the candidate
according to the checking result; anddetermining whether the hit
weighting of the candidate meets a criterion.

2. The synchronization method as claim in 1, wherein when the hit
weighting of at least one candidate meets the criterion, decoding the
bitstream.

3. The synchronization method as claim in 2, wherein the candidate meeting
the criterion is a frame start point of the bitstream.

4. The synchronization method as claim in 1, wherein the additional
information is a bit followed by the FAW pattern of the corresponding
candidate.

5. The synchronization method as claim in 1, wherein the hit weighting
corresponding to the candidate is increased when the FAW pattern
corresponding to the candidate exists and the additional information is
not against a valid sequence.

6. The synchronization method as claim in 1, wherein the hit weighting
corresponding to the candidate is decreased when the FAW pattern
corresponding to the candidate exists and the additional information is
not a valid sequence.

7. The synchronization method as claim in 1, wherein the hit weighting
corresponding to the candidate is reset when the FAW pattern
corresponding to the candidate does not exist.

8. The synchronization method as claim in 1, wherein when the FAW pattern
corresponding to the candidate does not exist, a first counter and a
second counter of the hit weighting corresponding to the candidate are
reset.

9. The synchronization method as claim in 1, wherein when the additional
information corresponding to the candidate is successive 0s, the
additional information is valid and a first counter of the hit weighting
is increased.

10. The synchronization method as claim in 1, wherein when the additional
information corresponding to the candidate is successive 1s, the
additional information is valid and a second counter of the hit weighting
is increased.

11. The synchronization method as claim in 1, wherein when the additional
information corresponding to the candidate is not successive 0s, the
additional informational is not valid and a first counter of the hit
weighting is reset or decreased.

12. The synchronization method as claim in 1, wherein when the additional
information corresponding to the candidate is not successive 1s, the
additional informational is not valid and a second counter of the hit
weighting is reset or decreased.

14. The synchronization method as claim in 1, wherein when the additional
information corresponding to the candidate is eight successive 0s and
eight successive 1s, the additional information corresponding to the
candidate is valid.

15. The synchronization method as claim in 1, wherein the criterion is the
FAW pattern corresponding to the candidate exists and the additional
information corresponding to the candidate is a sequence of 8 successive
0s and 8 successive 1s or 8 successive 1s and 8 successive 0s.

16. A multimedia data system, comprising:a demodulation unit demodulating
a bitstream to output a demodulated bitstream;a synchronization unit
receiving the demodulated bitstream, checking whether a FAW pattern
corresponding to a candidate of the bitstream exists, checking whether an
additional information corresponding to the candidate of the bitstream is
valid when the FAW pattern exists, determining a hit weighting
corresponding to the candidate according to the checking result,
determining whether the hit weighting of the candidate meets a criterion
and outputting a synchronization signal when the hit weighting meets the
criterion; anda decoding unit decoding the synchronization signal to
output a decoded bitstream.

17. The multimedia data system as claim in 16, wherein the hit weighting
corresponding to the candidate is increased when the FAW pattern
corresponding to the candidate exists and the additional information is
not against a valid sequence.

18. The multimedia data system as claim in 16, wherein the hit weighting
corresponding to the candidate is decreased when the FAW pattern
corresponding to the candidate exists and the additional information is
not a valid sequence.

19. The multimedia data system as claim in 16, wherein the hit weighting
corresponding to the candidate is reset when the FAW pattern
corresponding to the candidate does not exist.

20. The multimedia data system as claim in 16, wherein when the additional
information corresponding to the candidate is successive 0s, the
additional information is valid and a first counter of the hit weighting
is increased.

21. The multimedia data system as claim in 16, wherein when the additional
information for the candidate is successive 1s, the additional
information is valid and a second counter of the hit weighting is
increased.

22. The multimedia data system as claim in 16, wherein when the additional
information corresponding to the candidate is not successive 0s, the
additional information is not valid and a first counter of the hit
weighting is reset or decreased.

23. The multimedia data system as claim in 16, wherein when the additional
information corresponding to the candidate is not successive 1s, the
additional information is not valid and a second counter of the hit
weighting is reset or decreased.

24. The multimedia data system as claim in 16, wherein the bitstream
comprises a plurality of Near-Instantaneously Companded Audio Multiplex
(NICAM) frames and each NICAM frames comprises 728 candidates.

25. The multimedia data system as claim in 16, wherein the criterion is
the FAW pattern corresponding to the candidate exists and the additional
information corresponding to the candidate is a sequence of 8 successive
0s and 8 successive 1s or 8 successive 1s and 8 successive 0s.

Description:

BACKGROUND OF THE INVENTION

[0001]1. Field of the Invention

[0002]The invention relates to data synchronization, and more particularly
to multimedia data synchronization method and system utilizing additional
information.

[0003]2. Description of the Related Art

[0004]NICAM (Near Instantaneous Companded Audio Multiplex), an audio
multiplex system developed by the BBC, is used in PAL/SECAM TV
broadcasting in Europe and Asia. A general NICAM frame starts with an
8-bit "Frame Alignment Word" (FAW), followed by five control bits, eleven
bits of unprotected (no parity) additional data, and 704 bits of parity
checked data, represented as:

[0005]Five control bits (C0, C1, C2, C3, C4) are provided in each NICAM
frame. The first bit C0 is a frame flag used for synchronization of NICAM
frames, identifying the odd (C0=1) and even (C0=0) frames. The next three
bits C1, C2, and C3 are used to specify the mode of transmission. Table 1
shows the relationship between the mode of operation and the bits C1, C2
and C3. The fifth control bit C4, a reserve sound switching flag,
notifies the receiver if NICAM is lost. The receiver can then switch to
the frequency modulation (FM) mono sound signal.

[0006]FIG. 1 is a flowchart of a NICAM bitstream processing method. When a
NICAM bitstream is input, differential quaternary phase-shift keying
(DQPSK) demodulation is first performed (step S11) to determine whether
NICAM frames are synchronized (step S12). If not, the NICAM frames are
then synchronized (step S13), and the process proceeds to step S12. If
the NICAM frames are synchronized in step S12, the NICAM frames are
decoded to output the decoded NICAM bitstream (step S14).

[0007]Referring to FIG. 2, when the NICAM bitstream is received, it is
determined whether a FAW with 0x4E is detected. When N FAWs with 0x4E are
detected, decoding from the first frame begins. In the described process,
however, a bitstream buffer is required to store input data for decoding
from the first frame, decoding is not conducted in real time and false
alarms may frequently occur. Thus, it is desired to have a method for
fast and accurate synchronization.

BRIEF SUMMARY OF THE INVENTION

[0008]An embodiment of a synchronization method is provided. The
synchronization method comprises receiving a bitstream, checking whether
a FAW pattern corresponding to a candidate of the bitstream exists,
checking whether an additional information corresponding to the candidate
of the bitstream is valid when the FAW pattern exists, determining a hit
weighting corresponding to the candidate according to the checking result
and determining whether the hit weighting of the candidate meets a
criterion.

[0009]Another embodiment of a multimedia data system is provided. The
multimedia data system comprises a demodulation unit, a synchronization
unit and a decoding unit. The demodulation unit demodulates a bitstream
to output a demodulated bitstream. The synchronization unit receives the
demodulated bitstream, checks whether a FAW pattern corresponding to a
candidate of the bitstream exists, checks whether an additional
information corresponding to the candidate of the bitstream is valid when
the FAW pattern exists, determines a hit weighting corresponding to the
candidate when the additional information is valid, checks whether the
hit weighting meets a criterion and outputs a synchronization signal when
the hit weighting meets the criterion. The decoding unit decodes the
synchronization signal to output a decoded bitstream.

[0010]A detailed description is given in the following embodiments with
reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]The invention can be more fully understood by reading the subsequent
detailed description and examples with references made to the
accompanying drawings, wherein:

[0012]FIG. 1 is a flowchart of an NICAM bitstream processing method.

[0013]FIG. 2 is schematic view of locating FAWs for decoding an input
bitstream.

[0014]FIG. 3 is a flowchart of a multimedia data synchronization method
according to an embodiment of the invention.

[0016]FIG. 5 is a schematic diagram of a bitstream comprising a plurality
of NICAM frames according to another embodiment of the invention.

[0017]FIG. 6 is a schematic diagram of the hit weighting unit 600
according to another embodiment of the invention.

[0018]FIG. 7 is a schematic view of combinations of control bit Co
according to another embodiment of the invention.

[0019]FIG. 8 is a multimedia data system 800 according to another
embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0020]Several exemplary embodiments of the invention are described with
reference to FIGS. 4 through 8, which generally relate to multimedia data
synchronization. It is to be understood that the following disclosure
provides various different embodiments as examples for implementing
different features of the invention. Specific examples of components and
arrangements are described in the following to simplify the present
disclosure. These are, of course, are merely examples and are not
intended to be limiting. In addition, the present disclosure may repeat
reference numerals and/or letters in the various examples. This
repetition is for the purpose of simplicity and clarity and does not in
itself dictate a relationship between the various described embodiments
and/or configurations.

[0022]FIG. 3 is a flowchart of a multimedia data synchronization method
according to an embodiment of the invention. When a bitstream, such as a
NICAM bitstream, is input, each bit in a frame of the bitstream is a
candidate for a frame start point and a hit weighting for each candidate
is calculated for start point determination. A candidate with its
subsequent 7 bits are involved to check whether a FAW pattern
corresponding to the candidate exists or not (step S41). If the FAW
pattern (01001110, 0x4E) corresponding to the candidate does not exist,
the hit weighting corresponding to the candidate is reset (step S43) and
then a next candidate is checked whether FAW pattern exists or not (step
S41). If the FAW pattern (01001110, 0x4E) corresponding to the candidate
exists, additional information corresponding to the candidate is checked
(step S42). When the additional information corresponding to the
candidate is not valid, the hit weighting corresponding to the candidate
is reset (step S44) and then the next candidate is checked (going back to
step S41). In an embodiment of the invention, the additional information
is the first control bit C0 of each frame which is the 9th bit
counted from the candidate. FIG. 4 shows a 16-frame sequence of NICAM
bitstream. As shown, based on the NICAM specification, the control bit,
C0, of each NICAM frame are set to 1 for 8 successive frames, and, 0 for
the next 8 frames, thus, a 16-frame valid sequence is defined. Other
additional information, including frame synchronization word, sampling
rate, MPEG layer field, may also be utilized as the additional
information for more precise synchronization. If the additional
information corresponding to the candidate is valid, the hit weighting
corresponding to the candidate is determined or increased (step S45) and
then checked whether the hit weighting corresponding to the candidate
meets the criterion (step S46). If not, the next candidate is checked
(going back to step S41). If the hit weighting corresponding to the
candidate meets the criterion, synchronization of the bitstream is
completed (step S47). The candidate, which meets the criterion, is found
as a frame starting point of the bitstream and decoding of the bitstream
is performed accordingly.

[0023]FIG. 5 is a schematic diagram of a bitstream comprising a plurality
of NICAM frames according to another embodiment of the invention. The
bitstream comprises 1st frame, 2nd frame, and 3rd frame
and so on . . . . As described, since each NICAM frame comprises 728
bits, 728 candidates are provided for a frame starting point. The
starting point can be anywhere, for example, the first bit of 1st
frame, the second bit of 1st frame or the 728th bit of 1st
frame. Thus, a hit weighting for each corresponding candidate of each
frame is calculated for synchronization of the bitstream, wherein the
first candidate is the (728*n+1)th sample, the second candidate is
the (728*n+2)th sample, . . . , and the Kth candidate is
(728*n+k)th sample, where n≧0 and is an integer.

[0024]For example, if the first received bit SP is the 3rd bit of
1st frame, the first candidate is 3rd bit of 1st frame,
the second candidate is 4th bit of 1st frame, the 728th
candidate is 2nd of 2nd frame and so forth. When receiving the
3rd bit of 1st frame, the 3rd bit of 1st frame
together with the subsequent 7 bits, which are 3rd˜10th
bits of 1st frame, are checked to determine whether the FAW
corresponding to the 3rd bit of 1st frame exists or not (step
S41). To more specifically, the 3rd˜10th bits of 1st
frame are checked whether correspond to "01001110". Additional
information corresponding to the candidate, such as the control bit C0
which is the bit followed by the FAW pattern, is then checked to be valid
or not (step S42). In other words, the 9th bit counted from the
3rd bit of 1st frame, which is the 11th bit of 1st
frame is checked valid or not. As described, various additional
information can be utilized for synchronization, the following will take
control bit C0 as an example for further explain the operation of the
method of the invention. It is also noted that NICAM bitstream is
illustrated as examples but not to be limitative.

[0025]FIG. 6 is a schematic diagram of the hit weighting unit 600 for
calculating hit weightings of candidates according to another embodiment
of the invention. The hit weighting unit 600 comprising 728 sub weighting
units (1shw, 2shw . . . 728shw), wherein each sub
weighting unit calculates the hit weighting for a candidate. For example,
sub weighting unit 1shw calculates the hit weighting for the first
candidate, sub weighting unit 2shw calculates the hit weighting for
the second candidate, and so forth. Each sub weighting unit (1shw,
2shw . . . 728shw) comprises two counters 1A˜728A and
1B˜728B for recording the additional information check result of
corresponding candidate. The values of the counters 1A˜728A and
1B˜728B are determined according to the check result of the
additional information of corresponding candidate when the FAW (01001110,
0x4E) pattern corresponding to the candidate exists. Conversely, the
counters 1A˜728A and 1B˜728B are reset when the FAW pattern
corresponding to the candidate does not exist. To determine whether the
additional information is valid, control bits C0 of 16 frames are
involved for checking whether it is a valid control bit sequence. If a
16-frame sequence for the input bitstream provides 8 successive frames
with each control bit set to 0 and 8 successive frames with each control
bit set to 1, the additional information is valid. Hence, according to an
exemplary embodiment, when the additional information is successive 0s,
the counter of corresponding candidate (1A, 2A . . . or 728A) is
increased. Similarly, when the additional information is successive is,
the counter of corresponding candidate (1B, 2B, . . . , or 728B) is
increased. When the additional information is not successive 8 0s
(without change 0 to 1 one time), the additional information is not valid
and the counter (1A, 2A . . . , or 728A) is reset or decreased. When the
additional information is not successive 8 1s (without change 1 to 0 one
time), the additional information is not valid and the counter (1B, 2B .
. . , or 728B) is reset or decreased.

[0026]The values of the two counters of each candidate are checked to
determine whether a candidate meets the criterion. The synchronization is
complete when one of candidates meets the criterion. To summarize above,
the criterion is met when the hit weighting calculated by the sub
weighting unit of the candidate indicates that 16 FAW patterns
corresponding to the candidate are found and the sequence of control bit
C0, corresponding to the candidate, is valid where 8 successive C0 bits
are equal to 0 and another 8 successive C0 bits are equal to 1. The
bitstream is further decoded when synchronization is completed.

[0027]According to another embodiment of the invention, the hit weighting
corresponding to the candidate is increased when the FAW pattern exists
and the additional information is not against a valid sequence. The hit
weighting corresponding to the candidate is decreased when the FAW
pattern exists and the additional information is not a valid sequence.
The hit weight corresponding to the candidate is reset when the FAW
pattern corresponding to the candidate does not exist. When the criterion
has met a predetermined value for one of the candidates, synchronization
is completed and then the bitstream is decoded.

[0028]FIG. 7 is a schematic view of valid sequence of control bit values
Co according to another embodiment of the invention. According to an
embodiment of the invention, checking 11648 (16 frames) successive bits
from the starting point SP for synchronization. The valid sequence of
control bit values (additional information) C0 bits comprises
0000000011111111, 1111111100000000, 1100000000111111, 0000111111110000,
and others. The first and second valid sequences comprise 8 successive Co
equal to 0 and another 8 successive Co equal to 1 which corresponds to
the criterion. The third valid sequence comprises 8 successive C0 bits
equal to 1, counted from the 11-16 C0 bits to the 1-2 C0 bits, and
another 8 successive C0 bits equal to 0, which also corresponds to the
criterion. The fourth valid sequence comprises 8 successive C0 bits equal
to 0, counted from the 13-16 C0 bits to the 1-4 C0 bits, and another 8
successive C0 bits equal to 1, which also corresponds to the criterion.
Other combination comprise 8 successive Co equal to 0 and 8 Co equal to 1
or 8 successive Co equal to 1 and 8 Co equal to 0 which also meets the
criterion.

[0030]Further, a television or playback comprises demodulation unit 810
synchronization unit 820 and decoding unit 830 according to another
embodiment of the invention.

[0031]The invention provides a multimedia data synchronization method and
system, which uses less memory and does not require input data to be kept
during synchronization. Additionally, when synchronization is completed,
the decoding is performed immediately, eliminating processing delay.

[0032]The above embodiments of the method and system are also suitable for
a constant bit rate bitstream, comprising a DTV transport stream of DTV,
MP2, AC3, NICAM, and others.

[0033]While the invention has been described by way of example and in
terms of the preferred embodiments, it is to be understood that the
invention is not limited to the disclosed embodiments. To the contrary,
it is intended to cover various modifications and similar arrangements
(as would be apparent to those skilled in the art). Therefore, the scope
of the appended claims should be accorded the broadest interpretation so
as to encompass all such modifications and similar arrangements.